Rice mutants, selected under severe drought stress, show reduced stomatal density and improved water use efficiency under restricted water conditions

IntroductionRice is among the least water-use-efficient crops, and rice plants utilise most of their water uptake for transpirational cooling via stomata. To improve water-use efficiency (WUE) in rice, reducing stomatal density and size could help optimise transpiration and photosynthesis. MethodologyIn this study, we compared two series of purple rice stomata mutants: the Stomatal Model Mutant (SMM) identified by microscopic observation of flag-leaf stomata, and the Drought-selected Model Mutant (DMM) generated through screening under severe water stress. After undergoing two rounds of severe water stress between -60 to -80 Ym, right before the R1–2 reproductive stage, three DMMs were selected based on their rapid recovery rate and % filled-grain percentage.ResultThe three DMMs displayed 618–697 stomatal units per mm2, similar to the SMMs low-density stomata mutant (JHN 8756 (LD)). Furthermore, the four SMMs, three DMMs and the Jao Hom Nin wild type (JHN WT) were treated with two restricted water condition schemes from seedlings to harvest. The total amount of irrigation and precipitation during the experiment was 78.1 L/plant (69.1 mm/plant) for the less restricted water condition (LR) and 47.5 L/plant (42 mm/plant) for the more restricted water condition (MR). Water condition treatments had no effects on stomatal density and stomatal index. In contrast, genotypes and restricted water condition schemes affected plant height, tillers/plant, % filled grains and shoot dry weight (SDW). The three DMMs and the JHN 8756 (LD), the SMM's low-density stomata mutant, displayed greater resilience towards more restricted water conditions than the SMMs and the JHN wild type. Particularly, DMMs were tolerant to more restricted water condition treatments, showing no SDW penalties. Together, the DMMs and the JHN 8756 (LD) displayed higher WUE under these conditions of more restricted water conditions. ConclusionA rigorous screening process to distinguish tolerant mutants with a rapid drought recovery rate from severe water stress could pave the way to isolate more mutants with better stomatal functionality and resilience in preparation for imminent climate changes

Composition and Expression of Conserved MicroRNA Genes in Diploid Cotton (Gossypium) Species

MicroRNAs are ubiquitous in plant genomes but vary greatly in their abundance within and conservation among plant lineages. To gain insight into the evolutionary birth/death dynamics of microRNA families, we sequenced small RNA and 50-end PARE libraries generated from two closely related species of Gossypium. Here, we demonstrate that 33 microRNA families, with similar copy numbers and average evolutionary rates, are conserved in the two congeneric cottons. Analysis of the presence/absence of these microRNA families in other land plants sheds light on their depth of phylogenetic origin and lineage-specific loss/gain. Conserved microRNA families in Gossypium exhibit a striking interspecific asymmetry in expression, potentially connected to relative proximity to neighboring transposable elements. A complex correlated expression pattern of microRNA target genes with their controlling microRNAs indicates that possible functional divergence of conserved microRNA families can also exist even within a single plant genus

The asparagus genome sheds light on the origin and evolution of a young Y chromosome

Several models have been proposed to explain the emergence of sex chromosomes. Here, through comparative genomics and mutant analysis, Harkess et al. show that linked but separate genes on the Y chromosome are responsible for sex determination in Asparagus, supporting a two-gene model for sex chromosome evolution

Ozone-Ultrafine Bubbles for Reducing Concentration of Citric Acid and Sodium Chloride for Trimmed Young Coconut Preservation

Citric acid (CA) and sodium chloride (NaCl) are used in organically trimmed young aromatic coconuts to prevent microbial growth and browning. However, the use of high concentrations of these chemicals is considered a waste and may elicit allergic reactions in the operator. This study aimed to reduce the concentration of these two substances by using a combination of ozone-ultrafine bubbles (O3UFBs). The trimmed young coconuts were dipped in 20% CA + 20% NaCl (commercial method; C20N20), 20% CA + 10% NaCl + O3UFBs (C20N10-O3UFBs), and 15% CA + 15% NaCl + O3UFBs (C15N15-O3UFBs) for one minute. All the coconuts were wrapped with PVC film and stored at 2–4 °C for 30 days and then transferred to storage at 8–10 °C for 7 days. The quality of the coconut water and coconut meat was evaluated. The whiteness, browning index, polyphenol oxidase (PPO) activity, and total phenolic content of coconut mesocarp were investigated. Titratable acidity and the total soluble solid content of coconut water were 0.038–0.095% and 6.65–7.40 °Brix, respectively, while that of the coconut meat was 0.044–0.104% and 8.00–9.80 °Brix, respectively. The mesocarp whiteness, browning index, disease score, fruit appearance, PPO activity, and total phenolic content did not differ among the treatments. C20N10-O3UFBs and C15N15-O3UFBs treatments also controlled microbial growth and the surface browning of the trimmed coconuts. In conclusion, the use of O3UFBs decreased the concentration of CA and NaCl by at least 25% of the commercial method used for treating trimmed young coconuts

Extensive Families of miRNAs and PHAS Loci in Norway Spruce Demonstrate the Origins of Complex phasiRNA Networks in Seed Plants.

In eudicot plants, the miR482/miR2118 superfamily regulates and instigates the production of phased secondary small interfering RNAs (siRNAs) from NB-LRR (nucleotide binding leucine-rich repeat) genes that encode disease resistance proteins. In grasses, this miRNA family triggers siRNA production specifically in reproductive tissues from long noncoding RNAs. To understand this functional divergence, we examined the small RNA population in the ancient gymnosperm Norway spruce (Picea abies). As many as 41 miRNA families in spruce were found to trigger phasiRNA (phased, secondary siRNAs) production from diverse PHAS loci, with a remarkable 19 miRNA families capable of targeting over 750 NB-LRR genes to generate phasiRNAs. miR482/miR2118, encoded in spruce by at least 24 precursor loci, targets not only NB-LRR genes to trigger phasiRNA production (as in eudicots) but also noncoding PHAS loci, generating phasiRNAs preferentially in male or female cones, reminiscent of its role in the grasses. These data suggest a dual function of miR482/miR2118 present in gymnosperms that was selectively yet divergently retained in flowering plants. A few MIR482/MIR2118 precursors possess an extremely long stem-loop structure, one arm of which shows significant sequence similarity to spruce NB-LRR genes, suggestive of an evolutionary origin from NB-LRR genes through gene duplication. We also characterized an expanded miR390-TAS3 (TRANS-ACTING SIRNA GENE 3)-ARF (AUXIN RESPONSIVE FACTOR) pathway, comprising 18 TAS3 genes of diverse features. Finally, we annotated spruce miRNAs and their targets. Taken together, these data expand our understanding of phasiRNA network in plants and the evolution of plant miRNAs, particularly miR482/miR2118 and its functional diversification

Short communication: Algal leaf spot associated with Cephaleuros virescens (Trentepohliales, Ulvophyceae) on Nephelium lappaceum in Thailand

Abstract. Sunpapao A, Pitaloka MK, Arikit S. 2015. Algal leaf spot associated with Cephaleuros virescens (Trentepohliales, Ulvophyceae) on Nephelium lappaceum in Thailand. Biodiversitas 17: 31-35. Algal leaf spot disease of Nephelium lappaceum (rambutan) was observed in southern Thailand. The algae were isolated on Bold’s basal medium (BBM) and identified based on appearance of the lesions, algal morphology and molecular properties. Characteristics of the filamentous thallus cells, sporangiophores, sporangia, gametes and zoospores were clarified. A portion of the 18S small subunit rRNA was amplified to validate the morphological identification by sequence similarity. To summarize the main results, the plant parasite causing algal leaf spot was identified as Cephaleuros virescens, and in sequencing-based phylogenetic analysis the Cephaleuros PSU-R5.1 isolate from rambutan grouped with the algae in genus Cephaleuros. This confirms C. virescens as a causal organism of algal leaf spot disease on rambutan in southern Thailand

Morphological and molecular identification of Neopestalotiopsis clavispora causing flower blight on Anthurium andraeanum in Thailand

Flower blight on anthurium (Anthurium andraeanum) was observed during August 2018 on an anthurium cultivation farm in the Songkhla Province of southern Thailand. The fungal isolate was identified as Neopestalotiopsis clavispora based on the morphology and DNA sequence of the internal transcribed spacer (ITS), translation elongation factor 1-α (tef1-α), and β-tubulin (tub) genes. The phylogenetic tree, based on the combined sequences of ITS, tef1-α, and tub, confirmed this pathogen as N. clavispora. Pathogenicity of the species was confirmed according to Koch's postulate: N. clavispora could infect anthurium. To the best of our knowledge, this is the first report of N. clavispora as a pathogen of anthurium

Accelerating haploid induction rate and haploid validation through marker-assisted selection for qhir1 and qhir8 in maize

Doubled haploid (DH) technology becomes more routinely applied in maize hybrid breeding. However, some issues in haploid induction and identification persist, requiring resolution to optimize DH production. Our objective was to implement simultaneous marker-assisted selection (MAS) for qhir1 (MTL/ZmPLA1/NLD) and qhir8 (ZmDMP) using TaqMan assay in F2 generation of four BHI306-derived tropical × temperate inducer families. We also aimed to assess their haploid induction rate (HIR) in the F3 generation as a phenotypic response to MAS. We highlighted remarkable increases in HIR of each inducer family. Genotypes carrying qhir1 and qhir8 exhibited 1 – 3-fold higher haploid frequency than those carrying only qhir1. Additionally, the qhir1 marker was employed for verifying putative haploid seedlings at 7 days after planting. Flow cytometric analysis served as the gold standard test to assess the accuracy of the R1-nj and the qhir1 marker. The qhir1 marker showed high accuracy and may be integrated in multiple haploid identifications at early seedling stage succeeding pre-haploid sorting via R1-nj marker